/*
 * Syntelos 'SX'
 * Copyright (C) 1998, 2007  John Pritchard.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 */
package syntelos.sx.methods;

import syntelos.sx.Request;
import syntelos.sx.Response;

import alto.io.Output;
import alto.lang.Buffer;
import alto.lang.Value;
import alto.sys.Reference;


/**
 * Single server atomic decrement of an index value.
 * 
 * @see Lock
 * @see Unlock
 * @see Inc
 * @see Value
 * @since 1.6
 */
public class Dec
    extends syntelos.sx.Response
{

    public Dec(){
        super();
    }


    public void respond(Request req)
        throws java.io.IOException,
               java.lang.InterruptedException
    {
        if (this.isAuthenticated()){
            Reference reference;
            if (request.hasNotReference())
                reference = Request.ReferenceToIndex(req);
            else
                reference = req.getReference();

            Value value;
            try {
                reference.lockWriteEnter();
                value = Value.Dereference(reference);
                if (null != value)
                    value = value.subtract(Value.ONE);
                else 
                    value = Value.ZERO;
                //
                reference.setBufferFrom(value);
            }
            finally {
                reference.lockWriteExit();
            }
            
            alto.lang.buffer.Abstract iob = this.getCreateBuffer();
            alto.lang.buffer.OutputStream bout = (alto.lang.buffer.OutputStream)iob.openOutput();
            bout.println(value.toString());
            this.setStatusOk();
        }
        else
            this.setStatusUnauthorized();
    }

}
